Heritability and educational policy: Genetic and environmental effects on IQ, aptitude and achievement

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Abstract
Some common beliefs about the fairness of achievement tests, in comparison with IQ tests, and about the role of genetic differences among individuals and social‐class groups in determining academic achievement are challenged by a study investigating the effects of family background on adolescents’ IQ, aptitude, and school achievement tests scores. The study included 115 adoptive families with adolescent children, adopted in the first few months of life, and a comparison sample of 120 biological families with their own adolescent offspring. Both sample of families ranged from solid working to upper‐middle class. Results of the study revealed that differences among social‐class environments have little effect on IQ scores but larger effects on school‐achievement scores. Contrary to the beliefs of many school personnel, working‐class adolescents are at a greater disadvantage relative to upper‐middle‐class adolescents when the tests sample recently taught material. Genetic differences among individuals and among social‐class groups were found to be approximately the same for all types of tests. Some implications of the correlation between social class and achievement test scores and the consistent genetic differences in test scores for educational policy arc discussed.